IV.

Wittgenstein and the Logical Positivists

Russell’s work in mathematics attracted to Cambridge the Austrian philosopher Ludwig Wittgenstein, who became a central figure in the analytic and linguistic movement. In his first major work, Tractatus Logico-Philosophicus (1921; trans. 1922), in which he first presented his theory of language, Wittgenstein argued that “all philosophy is a ‘critique of language’” and that “philosophy aims at the logical clarification of thoughts”. The results of Wittgenstein’s analysis resembled Russell’s logical atomism. The world, he argued, is ultimately composed of simple facts, which it is the purpose of language to picture. To be meaningful, statements about the world must be reducible to linguistic utterances that have a structure similar to the simple facts pictured. In this early Wittgensteinian analysis, only propositions that picture facts—the propositions of science—are considered factually meaningful. Metaphysical, theological, and ethical sentences are judged to be factually meaningless.

Influenced by Russell, Wittgenstein, Ernst Mach, and others, a group of philosophers and mathematicians in Vienna in the 1920s initiated the movement known as logical positivism. Led by Moritz Schlick and Rudolf Carnap, the Vienna Circle initiated one of the most important chapters in the history of analytic and linguistic philosophy. According to the positivists, the task of philosophy is the clarification of meaning, not the discovery of new facts (the job of science) or the construction of comprehensive accounts of reality (the misguided pursuit of traditional metaphysics).

The positivists divided all meaningful assertions into two classes: analytic propositions and empirically verifiable ones. Analytic propositions, which include the propositions of logic and mathematics, are statements the truth or falsity of which depend altogether on the meanings of the terms constituting the statement. An example would be the proposition “two plus two equals four”. The second class of meaningful propositions includes all statements about the world that can be verified, at least in principle, by sense experience. Indeed, the meaning of such propositions is identified with the empirical method of verification. This verifiability theory of meaning, the positivists concluded, would demonstrate that scientific statements are genuine factual claims and that metaphysical, religious, and ethical sentences are factually empty. The ideas of logical positivism were made popular in England by the publication of Language, Truth and Logic by A. J. Ayer in 1936. In the field of ethics, the logical positivists argued that although ethical statements had no factual content, they served to express the emotions of the speaker. This theory, known as the emotivist theory of ethics, had its roots in Hume’s philosophy.